1. Field of the Invention
The present invention relates to a method of tandem welding type continuous rolling which conducts continuous rolling of a plurality of billets while joining them together in series by welding and an apparatus therefor.
2. Description of the Related Art
A known continuous rolling method to produce wire, rod, or shape steel with energy-saving and high efficiency comprises the steps of discharging billets from a heating furnace one at a time, welding the rear end of a preceding billet with the front end of a succeeding billet using a single unit of travelling flash-butt welder, removing the burr from the welded portions using a scarfer or the like, the thus formed continuous billet to a temperature necessary for rolling in an induction heating furnace, and continuously rolling the continuous billet in a rolling mill group: (disclosed in, for example, unexamined Japanese patent publication No.52-43754(1977)). Alternatively, there is a continuous rolling method in which billets discharged from a heating furnace are joined together by welding to form a continuous billet, and the continuous billet is heated again in the heating furnace, wherein a single unit of travelling flash-butt welder is used: (disclosed in, for example, examined Japanese patent publication No.52-11722(1982).
Shortening the cycle time for treating a single billet is an important issue in the continuous rolling of billets. In this respect, the weight of an ordinary billet is in a range of from 0.5 to 2 ton, and necessary cycle time to treat a single billet is within 1 min. to assure the production capacity of 70 to 80 ton/hr or more. Since conventional continuous rolling processes use only one on-line travelling flash-butt welder, as described above, the welding time inherent to the travelling flash-butt welder is difficult to shorten. Consequently, it is impossible to actualize the cycle time of less than 1 min. in the prior art.